The present invention relates to the use of certain alkaline earth metal salts as auxiliary agents in chemical mechanical polishing (CMP method), particularly of microelectronic components.
In certain fields of the industry, components are often needed that have been polished to a certain profile on at least one side. For example, the components may need to be uniformly flat and have a low surface roughness. Components which may need polishing include, for example, optical components, semiconductor components and ceramics.
One method of manufacturing such components with a high degree of polish is the chemical mechanical polishing (CMP) method using polishing slurries. Chemical mechanical polishing is usually performed as described below. The workpiece to be polished, e.g., a silicon wafer, is positioned with the surface to be polished facing down on a rotating pressure plate (platen). The wafer is secured by a carrier. The wafer and platen rotate in the same direction. A polishing pad or polishing substrate with a polishing slurry is provided on the surface of the platen. The polishing slurry contains very fine abrasives such as silicon dioxide or cerium oxide.
When oxide layers are to be polished, a basic slurry is generally used, e.g., a slurry containing potassium hydroxide solution or ammonia water and having a pH in the range from 10 to 11. To polish metals such as tungsten, slurries which typically contain an oxidizing agent such as hydrogen peroxide and have a low pH, e.g., from 0.5 to 4, are used. U.S. Pat. No. 5,695,384 discloses the use of slurries in the neutral pH range, using colloidal silicon dioxide to which a soluble halide salt, e.g., sodium chloride has been added. Ceramics such as barium strontium titanate as well as other materials such as gallium arsenide, diamond, silicon carbide and other perovskite materials can be polished with such slurries.